This invention relates to pressure sensitive adhesives (PSA's) and more particularly to radiation-friendly resins for use therein and to process improvements for making such resins.
PSA's are widely used in medical applications such as, for example, adhering a bandage to the skin of a patient. In one approach to preparing the bandage, liquid PSA is coated on a release liner, then the liquid is evaporated and the dry coating of pressure sensitive resin (sometimes referred to herein as "pressure sensitive interpolymer") transferred to a bandage substrate. The components of the medical formulation are next applied to the exposed coating followed by covering with another release layer to form the bandage. In use the covering is peeled away and the bandage pressed against and held on the skin by the pressure sensitive resin of the PSA.
Sterilizing the bandage for hygenic purposes to kill bacteria before use is standard practice, with exposure to radiation such as electron beam being used for procedural simplicity. Prior art adhesive compositions, however, are radiation-sensitive in that their strength properties are adversely affected, typically becoming too brittle, resulting in weak adherence of the bandage to the user's skin. Inclusion of additives in the PSA formulation intended to scavenge undesirable by-products generated during irradiation have been unsuccessful since adversely affecting peel adhesion of the PSA.